The present invention is generally directed to a telecommunication system which supports both conventional telephones connected by wire communication channels to a central office switch and wireless telephones coupled by wireless communication channels to base stations which are, in turn, coupled by wire communication channels to the telecommunication system. The present invention is more specifically directed to an apparatus and method which permits an in-progress telephone call to either a wire or wireless telephone to be transferred to the other without requiring additional action by the telecommunications switch.
Relatively inexpensive wireless telephone sets known as "cordless" telephones are available for use primarily in homes and consist of a base unit connected as an extension phone and a portable handset coupled by an RF communication channel with the base unit. Although a wireless communication channel is involved for cordless telephones, they function essentially as a conventional telephone connected by a long extension cord. That is, the base units of such telephone sets provide limited range and are not designed to support a plurality of subscribers with concurrent available wireless channels. Cordless telephones are connected in parallel with wired telephones resulting in a decrease in signal (audio) level and undesired impedance termination of the line when the cordless and a wired telephone are off-hook or active at the same time.
Conventional cellular communication systems issue a telephone number for a user's wireless telephone which differs from the same user's conventional wired telephone. This may require a party desiring to call the user to call both the wired and wireless telephone numbers in order to reach a particular party. Also, consider the situation in an office environment in which a user is engaged in a telephone conversation using a conventional wired telephone and has to leave the office to travel to another location in the building. Even if such a user also had a wireless telephone, the user could not continue the existing conversation by transferring to his wireless telephone without reestablishing another connection (separate call) to the same party since conventional cellular wireless communication systems do not permit a transfer of an existing conversation between wired and wireless telephones.